There are several methods for producing security keys. These methods disclose mechanical, magnetic and micro-processor devices, which have all been used to secure an entry point.
Mechanical locking systems, in which a key is used to turn a locking device between a locked state and an unlocked state, are very simple and inexpensive systems. However, people such as safebreakers can easily tamper with them. The keys can be copied conveniently in stores and locks are labor-intensive to change, both of which lower the security of a mechanical system.
Magnetic systems involve the use of magnets both in the key and the locking mechanism. Locks are locked or unlocked by the turning of the magnetic pieces within the locking mechanism. Magnetic systems can be problematic because of the degradation of the key (loss of magnetic force) in the presence of ferromagnetic objects or heat. They are also not high in security due to the limited number of magnetic combinations and the ease in copying a magnetic key.
Electronic devices use a keypad, a micro-processor and memory and are opened by depressing the correct sequence of numeric keys. The system is advantageous due to the lack of a separate key and large number of possible combinations; however, the system loses security as the keypad wears and the system is costly to implement.
There are several patents that attempt to address the problems above. U.S. Pat. No. 5,838,232 describes a multi-purpose locking device including a key made of a synthetic resin. The key includes a plurality of fine apertures and block members. Light receiving positions are set by the apertures not closed by the block members whereas light shielding positions are set by the apertures closed by the block members. A logic unit determines whether or not the correct key has been placed in the keyhole by comparing the pattern of apertures to a correct pattern.
U.S. Pat. No. 4,837,425 describes a security arrangement that includes a token in the form of a thin lamina that co-operates with a receptor. The token includes an optically readable pattern in the form of a bar code and a reflector that deflects the light modified by the bar code onto the receptor's optical sensor. The system includes a comparator to compare the light detected signal with an independently provided reference signal.
U.S. Pat. No. 5,283,431 describes an optical key security system that utilizes gradient refractive materials in an access key. The non-duplicable key has five separate encoded segments. The segments are made of an optically transmissive material (plastic or glass) with a gradient refractive index and diffusive properties, which bend light in ways which cannot be duplicated by conventional materials. Infrared beams are passed through the segments and an imaging system detects the pattern, which is sent to a micro-processor for pattern comparison.
Each of the aforementioned patents describes a unique key that is relatively inexpensive, difficult to duplicate, is not easily compromised by ferromagnetism or heat and has a large number of possible key patterns. These are important for temporary keys in places such as hotels, where keys are exchanged frequently. Hotel keys should be easily (simply yet securely) programmed by the management, having a large number of combinations, should be light weight, simple to dispense and low in cost. An advantage not currently found in the prior art, which would be beneficial to a broad spectrum of industries, is the capability of creating a key which is both difficult to duplicate and can be created on-demand. The present invention has this capability and as well provides a lightweight, inexpensive solution.